Preexisting mental disorder and mortality among people with traumatic spinal injury: a population-based retrospective cohort study

BACKGROUND: Both mental disorders and traumatic spinal injury are associated with premature mortality. However, relatively little is known about the impact of preexisting mental disorders on mortality risk following traumatic spinal injury (TSI). OBJECTIVES: We aimed to evaluate the rates and relative risk of mortality after acute TSI by preexisting mental disorder status, compared to the general population, and stratified by age at injury. METHODS: Individuals with acute TSI were identified from hospital records in New South Wales, Australia, and linked with ambulance and emergency department records from 1st June 2013 to 30th June 2016. Death records were linked from 1st June 2013 until 31st December 2018. We calculated all-cause and cause-specific crude mortality rates, age- and sex-adjusted standardised mortality ratios, and modelled the association between preexisting mental disorder and mortality by fitting flexible parametric survival models, stratified by age (16-64 and ≥65 years). RESULTS: 23% of the cohort had mental illness only, 6% had substance use disorder (SUD) only, and 5% had a dual diagnosis of mental illness and SUD. The crude mortality rate was 84.1 (95% CI 81.8-86.5) deaths per 1 000 person-years. Compared to the general population, the younger age stratum for those with dual diagnosis (standardised mortality ratio, SMR = 17.6; 95% CI 14.1-21.9), SUD only (SMR = 9.2; 95% CI 7.3-11.7), and mental illness only (SMR = 4.4; 95% CI 3.3-5.8) had markedly elevated mortality. Compared to those without mental disorder, all mental disorder groups were at increased risk of mortality after TSI, except for the mental illness only group in the younger age stratum. CONCLUSIONS: Preexisting mental disorders are associated with increased mortality after TSI, and markedly so for individuals aged 16-64 years. Increased integration with mental healthcare and addiction medicine is likely critical for reducing health disparities for those with mental disorders after TSI. DATA REGISTRATION: This is an observational study that used routinely-collected administrative data from New South Wales, Australia. These data are subject to ethical and data privacy requirements that preclude making them publicly available. Therefore, we cannot share and register them in international data repositories.